How do I change the email linked to my Avast account?

I recently renewed my Avast however my old comcast email in the account has been deleted. How do I change the email my account is linked to?

Use the my.avast.com account to add a new email address. You will most likely get an email to confirm this address. When confirmed, you should be able to set the new email address as the default email - you should be able to remove the old defunct email address.